This invention relates in general to apparatus for sensing and controlling the water level of a swimming pool, and more particularly to control circuitry for automatically controlling the level of water in the swimming pool in response to a plurality of water level sensing positions which directly sense the level of the pool water with the circuitry compensating for wave action in the pool, resistance responsive oscillators detecting the presence or absence of water at each respective sensor level, by a change in magnitude of oscillation, and monitoring circuitry to detect an improper sequence in the signals representative of the sensing levels to disable the water fill means for the pool.
Various means of automatically controlling the water level of a swimming pool are known to the prior art. Many of these water level control systems utilize a water level sensing chamber or tube disposed remotely from the pool to eliminate spurious detection of abnormally high or abnormally low water level conditions due to the wave action of the water in the pool such as those caused by swimmers, weather or other disturbances to the surface of the water. These isolated or remote sensing tubes or chambers must be specially constructed to accurately reflect the water level in the pool and yet effectively eliminate disturbances in the pool water level. A tube or conduit of narrow internal diameter is often provided for this purpose to limit the amount of water communicating between the pool and the sensing chamber. However, due to its small internal diameter, such tubes are prone to plugging or other blockage by debris which falls into the pool and control over the level of the water in the pool is thereafter lost. Other limitations of the sensing chamber, such as water leakage or improper venting, also reduce the reliability of sensing the pool level in this manner.
Reliability problems often occur with electronically sensing and controlling the water level of a pool. It is usually desirable to have the control circuitry at a location in proximity to the pool to avoid lengthy routing of wiring to or from other components of the water level control system. The control circuitry is therefore often located relatively close to the pool in a location which not infrequently becomes damp or experiences high humidity levels. Malfunctions in electronic circuitry can often occur under high humidity conditions, especially where sensing of the water level is dependent upon measuring of the impedance at a probe or contact. Such a malfunction can cause the circuitry to incorrectly operate the water fill valve, the water dump valve or the water circulating pump to result in an undesired pool water level.
It is therefore a principal object of the present invention to provide novel and improved control circuitry adapted to directly sense and more effectively control the water level in the swimming pool.
Another object of the invention is to eliminate spurious water level signals which are caused by wave action or other water surface disturbance such that the water fill or dump apparatus is not intermittently activated or de-activated.
Yet another object is to provide for sensing of the water level by means of a low voltage A.C. signal generated by a resistance responsive oscillator which changes in oscillator signal amplitude in response to the presence or absence of water at an associated electrode contact of the sensor.
Another object of the invention is to provide water level sensing and controlling circuitry having a higher reliability than heretofore available.
Further object of the present invention is to provide malfunction detecting circuitry capable of sensing and monitoring the various sensor levels and the sequencing of the electrical signals derived therefrom to disable the swimming pool water fill valve and the water circulating pump upon the occurrence of a malfunction.
These advantages of the invention, and others, including those inherent in the invention are provided by control circuitry adapted for electrical connection to a water level sensor having four vertically spaced apart water level sensing positions, said water levels including, in order of increasing elevation, a low level, a latch level, a normal level, and a high level. A resistance responsive low-voltage A.C. oscillator associated with each of the level sensing positions changes in oscillator signal amplitude to produce a change in output state responsive to the presence or absence of water in the pool at the respective sensor level. Threshold detecting circuitry changes in output in response to the magnitude of the oscillator signal. Delay circuitry in series with each oscillator and threshold detector operates to integrate a change in output state of the threshold detector such that the control circuitry is not responsive to wave action or other disturbance of the water surface in the pool. Water fill and dump conduits are electrically controlled by the control circuitry to fill or dump water from the pool in accordance with the levels sensed by the sensor. A monitoring portion of the control circuitry senses the sequencing and operation of the latch, normal and high sensor levels to disable the water fill conduit upon the occurrence of a control circuitry of sensor malfunction. The circuitry also includes bi-stable switch circuitry for controlling the water fill conduit to begin filling the pool if the water level at the sensor is below the latch level and to stop filling the pool when the water level has reached the normal level. The hysteresis provided by the bi-stable switch causes the water fill means to fill the pool for a given interval of time that it takes for the water to be raised from the latch to the normal level, rather than intermittently. An audible alarm is energized upon sensing a high water level condition and the alarm may be separately disabled.